In order to ensure that the temperature of at some point in an equipment does not exceed a safe operating limit, it has been customary to use a cooling fan operating at a speed required for the worst case situation determined by such factors as ambient temperature, line voltage, and in some electronic systems the electrical load applied to the system. The audible noise produced by operation in this manner can be very objectionable to the user of the equipment so that it would be advantageous to reduce the speed of the fan when circumstances permit. This can be effected by thermally coupling a temperature responsive impedance such as a thermistor to an appropriate point in the equipment and controlling the speed of the fan in accordance with the temperature thereof. When the fan is driven by a D.C. motor, its speed can be easily controlled by varying the voltage applied to the motor as a function of the value of the temperature responsive impedance, but when the fan is driven by an A.C. motor, variation in speed is usually achieved by a phase control circuit that produces electrical noise, EMI/RFI. Unfortunately, the noise may have an adverse effect on the performance of nearby circuits that may be in the equipment being cooled or in other equipment. The electrical noise can also prevent the apparatus from passing radiation limits mandated by regulatory agencies such as the FCC in the U.S.A. or the VDE in Germany.